Cancer is the second leading cause of death, resulting in one out of every four deaths in the United States. In 1997, the estimated total number of new diagnoses for lung, breast, prostate, colorectal and ovarian cancer was approximately two million. Due to the ever increasing aging population in the United States, it is reasonable to expect that rates of cancer incidence will continue to grow.
Cancer is a disease which involves the uncontrolled growth (i.e., division) of cells. Some of the known mechanisms which contribute to the uncontrolled proliferation of cancer cells include growth factor independence, failure to detect genomic mutation, and inappropriate cell signaling. The ability of cancer cells to ignore normal growth controls may result in an increased rate of proliferation. Although the causes of cancer have not been firmly established, there are some factors known to contribute, or at least predispose a subject, to cancer. Such factors include particular genetic mutations (e.g., BRCA gene mutation for breast cancer, APC for colon cancer), exposure to suspected cancer-causing agents, or carcinogens (e.g., asbestos, UV radiation) and familial disposition for particular cancers such as breast cancer.
Cancer is currently treated using a variety of modalities including surgery, radiation therapy and chemotherapy. The choice of treatment modality will depend upon the type, location and dissemination of the cancer. For example, surgery and radiation therapy may be more appropriate in the case of solid well-defined tumor masses and less practical in the case of non-solid tumor cancers such as leukemia and lymphoma. One of the advantages of surgery and radiation therapy is the ability to control to some extent the impact of the therapy, and thus to limit the toxicity to normal tissues in the body. However, surgery and radiation therapy are often followed by chemotherapy to guard against any remaining or radio-resistant cancer cells. Chemotherapy is also the most appropriate treatment for disseminated cancers such as leukemia and lymphoma as well as metastases.
More recently, the use of CpG containing nucleic acids has been proposed for the treatment and prevention of cancer. We have found that unmethylated CG-dinucleotides within certain sequence contexts (CpG DNA) are recognized by the vertebrate immune system as foreign DNA (bacterial or viral). CpG DNA activates a coordinated set of immune responses that include innate immunity (macrophages, dendritic cells, and natural killer cells), humoral immunity, and cellular immunity. Krieg A M et al., Pharmacol Ther 84:113-20 (1999); Krieg A M et al., Curr Top Microbiol Immunol 247:1-21 (2000); Wagner H, Adv Immunol 73:329-68 (1999). As a vaccine adjuvant, CpG DNA is at least as effective as the gold standard complete Freund's adjuvant (CFA), but induces higher Th1 activity and demonstrates less toxicity. Chu R S et al., J Exp Med 186:1623-31 (1997); Weiner G J et al., Proc Natl Acad Sci USA 94:10833-7 (1997); Roman M et al., Nat Med 3:849-54 (1997); Lipford G B et al., Eur J Immunol 27:2340-4 (1997); Davis H L et al., J Immunol 160:870-6 (1998). Recently, we identified a human CpG motif which triggers proliferation and activation of primary human B cells. Hartmann G et al., J Immunol 164:944-53 (2000).